In the LTE (Long Term Evolution) system, a mobile station UE # i determines, based on a formula shown in FIG. 5A, a transmission power PPUSCH,c(i) of PUSCH (Physical Uplink Shared Channel) in a cell (or CC: Component Carrier) # c for every TTI (Transmission Time Interval).
Among the variables included in the formula shown in FIG. 5A, PCMAX,c(i) is a maximum transmission power of the mobile station UE # i after considering a required power back-off in a cell # c; MPUSCH,c(i) is number of resource blocks assigned to the mobile station UE # i in the cell # c; Po PUSCH,c(j) is a standard electric-power offset value notified in the cell # c; αc(j) is an inclination value of Fractional TPC (Transmission Power Control) notified in the cell # c; PLc is a propagation loss (path loss) in the cell # c measured by the mobile station UE # i; ΔTF,c(i) is an electric-power offset value determined based on a modulation method and a coding rate used in the mobile station UE # i; and fc(i) is a correction value for closed loop power control used in the mobile station UE # i.
Among the variables included in the formula shown in FIG. 5A, the propagation loss PLc is unknown to a radio base station eNB. Therefore, when the propagation loss PLc changes, the mobile station UE # i feeds back PHR (Power Headroom Report) as shown in FIG. 5B.
PH is a difference between the maximum transmission power PCMAX,c(i) of the mobile station UE # i and a current transmission power PPUSCH,c(i) of the mobile station UE # i calculated by using the formula shown in FIG. 5A. The calculated difference may be a positive or a negative value.
Moreover, in a mobile communication system of the LTE system, as shown in FIGS. 6A and 6B, an overlaying configuration in which small cells are deployed on the coverage of a macrocell that uses an existing frequency (for example, 0.8/2 GHz) can be used.
The small cells, as shown in FIG. 6A, can operate at the same frequency as that of the macrocell, or can operate at a different frequency (for example, 3.5 GHz) from that of the macrocell, as shown in FIG. 6B.
Moreover, the small cells can be operated by a remote radio equipment (RRE) that is centrally controlled by a radio base station MeNB that controls the macrocell, or can be operated by a radio base station SeNB that differs from the radio base station MeNB, as shown in FIGS. 6A and 6B.
The radio base station MeNB and the radio base station SeNB are connected via a backhaul line, in which delay time cannot be ignored, and these radio base stations mutually exchange the information. A transmission delay of the backhaul can be up to few tens of microseconds.
Moreover, in Release-12 of the LTE system, CA (Carrier Aggregation) used till Release-10 of the LTE system has been expanded, and performing “Inter-eNB CA”, in which high throughput can be achieved by performing a simultaneous communication using cells (or CC) under the control of plural radio base stations eNB that are connected via the backhaul is being studied (see Non-Patent Document 1).